Low-power vehicle detection

ABSTRACT

A parking meter detects an object in proximity, based on a change in a proximity measurement at the meter, activates a directional sensor in response to detecting the object, receives sensor data at a meter processor from the directional sensor, wherein the received sensor data indicates a predetermined direction to the detected object relative to the meter. The parking meter determines a presence of the object, or lack thereof, in the predetermined direction based on the sensor data, and upon a positive determination of the presence of the object, stores an indication of the presence of the object along with a time of the positive determination.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/511,484, filed Jul. 25, 2011, which is hereby incorporated in itsentirety and for all purposes.

BACKGROUND

Solar and/or battery powered parking systems such as single-space ormulti-space meters for vehicles can employ parking meters with vehicledetection systems that detect the presence of a vehicle in a parkingspace. Time paid for parking in the space can then be dependent on thespace being occupied by a vehicle. One technique for detecting thepresence of a vehicle is to use a magnetometer located in the parkingspace. A magnetometer can be advantageous because it has relatively lowpower requirements, and often can be suitably powered by a battery. Amagnetometer must be located close to the vehicle that will occupy theparking space, for accurate detection without false indications.Placement of a magnetometer in a parking space typically requires coringof the surface asphalt or concrete (i.e., drilling a cylindrical openingor shaft) for embedding the magnetometer in the adjacent street orsidewalk area. This can be a very labor intensive and relativelyexpensive proposition.

Alternatively, a magnetometer could be included in a parking meter ofthe parking space, which would avoid the surface coring and embedding ofthe magnetometer. This placement will usually decrease the accuracy ofdetection, because magnetometers possess no directional detectioncapability. Because of the directional deficiency, a magnetometerinstalled in a meter potentially could not distinguish between a vehicleparked in the space associated with the parking meter and a vehicleparked in an adjacent parking space, or could not distinguish between avehicle parked in the space and a vehicle stopped in the street.

Other vehicle detection systems have employed ultrasonic or infraredsystems internal to a parking meter. Such systems send out a knownultrasonic or infrared signal and evaluate vehicle presence based onpartial reflection of the signal, or lack thereof. The signal can bemodulated for improved accuracy of detection. Because parking meters,especially single-space parking meters, usually have a limited powerbudget, these ultrasonic and infrared systems are designed to beoperated at relatively low power levels. Unfortunately, low-powerultrasonic and infrared systems are often prone to signal interference,due to pedestrian traffic, rain, snow, wind, and the like, and can havevery narrow angles of detection. Accuracy of detection can be improvedby increased signal power. Moreover, ultrasonic and infrared systemstypically require a relatively large percentage of the transmittedsignal to be reflected back for detecting the presence of a vehicle.Receiving a reflected signal that constitutes a large percentage of thetransmitted signal can be problematic, given weather conditions andpedestrian traffic, and therefore ultrasonic and infrared systems can beinherently unreliable as a means for detecting the presence of a vehiclein a parking space.

Other vehicle detection systems that potentially could be more accuratethan low-power magnetometers, ultrasonic systems, and infrared systems,include cameras, passive infrared systems (such as used in automaticdoor openers), active infrared detection, and radar. These othersystems, while possibly providing very accurate detection of a vehiclein a parking space, typically use more power than can be provided by abattery, solar cell, or other low-power system of a battery and/or solarpowered parking meter such as the single space meter described below.For example, radar can be very difficult to utilize because of powermanagement issues, and often provides relatively unpredictable results.

It should be apparent that accurate vehicle detection systems eitherrequire extensive installation and/or maintenance costs, as withembedded magnetometer systems, or are very inaccurate when placed adistance away from the object to be detected, or use too much power fora single-space parking meter in order to be suitable. In addition, adirectional sensor that is placed in the space to be monitored orexternal to a meter pole, may become compromised by dirt or debris, ormay fall victim to tampering. What is needed is a more reliable, lowpower vehicle detection system for use in a solar and/or battery poweredparking meter. The present invention satisfies this need.

SUMMARY

A parking meter detects an object in proximity, based on a change in aproximity measurement at the meter, activates a directional sensor inresponse to detecting the object, receives sensor data at a meterprocessor from the directional sensor, wherein the received sensor dataindicates a predetermined direction to the detected object relative tothe meter. The parking meter determines a presence of the object, orlack thereof, in the predetermined direction based on the sensor data,and upon a positive determination of the presence of the object, storesan indication of the presence of the object along with a time of thepositive determination.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating various embodiments, are intended for purposes ofillustration only and are not intended to limit the scope of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now described, by way of a non-limiting example, withreference to the accompanying drawings, where like reference numeralsrefer to like objects, and in which:

FIGS. 1A, 1B, and 1C are schematic illustrations of embodiments ofsingle space parking meters.

FIG. 2A shows a functional block diagram of a removable meter unit usedin the parking meter of FIG. 1A.

FIG. 2B shows a functional block diagram of a removable meter unit and atag device used in the parking meters of FIGS. 1B and 1C.

FIG. 3 shows an example of a local group of parking meters that employ alow power vehicle detection system in accordance with the disclosure.

FIG. 4 shows another example of a local group of parking meters thatemploy a low power vehicle detection system in accordance with thedisclosure.

DETAILED DESCRIPTION

A parking meter for a parking space associated with the parking meterutilizes a proximity sensor to detect an object in proximity to theparking space and in response activates a directional sensor to detectthe presence and direction of the object, such as a motor vehicle. Theproximity sensor is a low-power sensor that can detect an object inproximity to the sensor, but generally has insufficient sensitivity andprecision to identify the presence and direction of the object. Forexample, a low-power proximity sensor comprising a magnetometer candetect if a metallic object is in proximity to the magnetometer, but isgenerally incapable of detecting the direction in which the metallicobject is located in relation to the magnetometer. The directionalsensor typically draws more power than the proximity sensor and cancomprise a sensor such as, but not limited to, an infrared, passiveinfrared, radar, or optical sensor, which is capable of determining thepresence of an object in a specific direction relative to thehigher-powered directional sensor. Such directional sensors typicallyrequire greater power for operation than can be supplied continuously orperiodically by a typical power-limited device such as a single spaceparking meter. In accordance with the disclosure, the low-powerproximity sensor can comprise a magnetometer, which is used as a triggerto activate the directional sensor to receive sensor data. Thedirectional sensor data is analyzed to determine whether or not anobject detected by the low-power sensor is located in a specificlocation associated with the directional sensor. This constructionpermits the use of a relatively higher power directional sensor havinggreater accuracy, such that the directional sensor can be activated onlywhen needed, as indicated by the low-power sensor. This eliminates theneed for providing continuous or periodic power to the higher powerdirectional sensor.

In another aspect, after the directional sensor has verified thepresence of an object of interest, the magnetic signature captured bythe low-power sensor magnetometer can be inverted and used to determinethe departure of the object of interest from the parking space. Thedeparture indication can be used to reset any time remaining on theparking meter to zero or to some other desired amount of remaining time

In FIG. 1A, an embodiment of a single space parking meter in accordancewith this disclosure is designated generally by the reference numeral10-1. The parking meter 10-1 includes a location housing 2, a cashcollection box 4, and a meter unit 6. The location housing 2 is fixedlyattached to a pole 8 associated with a parking space at a geographiclocation, with the cash collection box 4 and the meter unit 6 beingreceived in the location housing. The meter unit 6 is a removable meterunit that can be replaced independently of other components of the meter10-1 such as the housing 2 and cash collection box 4. The cashcollection box 4 is also removable and can also be replacedindependently of the other meter components.

In FIG. 1B, another embodiment of a single space parking meter isdesignated generally by the reference numeral 10-2. The parking meter10-2 includes the location housing 2, the cash collection box 4, themeter unit 6, and an auxiliary device 3-1 in the form of a tag. The cashcollection box 4, the meter unit 6, and the tag 3-1 are received withinthe housing 2. The housing 2 is fixedly attached to the pole 8. The tag3-1 is permanently attached to an inner surface of the housing 2.Attachment to an inner surface shields the tag from the outsideenvironment and helps prevent damage and vandalism to the tag. The cashcollection box 4 and meter unit 6 are removable and replaceable. In theexample shown in FIG. 1B, the tag 3-1 is connectable to the meter unit 6by means of a length of wire 5 and a plug-in connector 7 at the meterunit, and can be powered by the meter unit (e.g., by a battery, solarcell, or other power source associated with the meter unit). The tag 3-1is useful for associating the collection box 4 and meter unit 6 with thelocation.

Referring to FIG. 1C, another embodiment of a single space parking meteris designated generally by the reference numeral 10-3. The parking meter10-3 is similar to the parking meter 10-2 of FIG. 1B except that theparking meter 10-3 includes a wireless tag 3-2 and the meter unit 6-2includes a wireless transceiver 9. The wireless tag 3-2 communicateswirelessly with the meter unit and can be, for example, an RFID tag, asmart card, an ID token, or the like. The wireless transceiver 9receives information from the tag 3-2 and, for example, can be a radiotransceiver that uses passive RFID technology, WiFi, Bluetooth, WiMax,or other short range wireless radio technology, in accordance with thewireless communication channel used by the tag.

The wireless transceiver 9 of the parking meter 10-3 may be an infrared(IR) transceiver that emits an infrared beam for data communication. Inthat case, the transceiver 9 is aligned with the tag 3-2 such that theinfrared beam of the transceiver is properly targeted at the tag 3-2.

In one embodiment, the wired tag 3-1 or the wireless tag 3-2 is used tomonitor the content of the cash collection box 4. Each tag 3 has aunique identifier that identifies the parking meter 10 with which it isused, and that is associated with a unique physical location where theparking meter is fixedly located, e.g., the location of the pole 8 andthe location housing 2. Each tag 3 has a unique ID which is transmittedto the central management system. The ID is logically connected in themanagement system's database to that meter pole 8 and location specificsettings. Therefore, the removable parking meter unit 6 may receive thecorrect hours of operation, rate tables, and other location-specificdata related to that meter pole 8 associated with a specific parkingspace.

The embodiment of the location housing 2 in FIGS. 1A, 1B, and 1C is asingle or dual space type of housing that is affixed to the pole 8 andis configured to mate with a removable meter unit 6. In otherembodiments, however, the location housing 2 can be a cabinet or otherenclosed space that is configured to mate with one or more removablemeter units, where the removable meter units are configured to be matedin compartments or sockets of the cabinet, such that each of thecompartments is associated with a physical location that is notnecessarily at the same location as the cabinet or the compartment. Inother embodiments, the location housing can be another type ofreceptacle fixedly placed and associated with a physical location.

FIG. 2A is a functional block diagram of a removable meter unit that canbe used in the meter 10-1 of FIG. 1A and is designated generally byreference numeral 6-1. The removable meter unit 6-1 includes a radiotransceiver 12, an antenna 14, a control module 16, a user interface 18through which payment can be received, a proximity sensor 20, and adirectional object sensor 22. The proximity sensor 20 is a low-power,non-directional, omnidirectional or multi-directional sensor such as amagnetometer, an optical sensor, a pressure sensor, an ultrasonicsensor, or the like, comprising a low-power sensor. As indicated above,the parking meter 10 is self-powered and, as described more fully below,uses the proximity sensor 20 and the directional object sensor 22 todetect a presence of a vehicle in a parking spot associated with theparking meter 10-1 and operates under control of the control module 16.Optionally, the directional object sensor 22 may be located outside themeter unit 6-1 and wirelessly connected to the meter unit 6-1 using alow power radio link. For example, a directional object sensor may beplaced on the pole 8 or on another pole or similar object.

The control module 16 includes one or more processors such asapplication specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, micro-controllers, microprocessors,other electronic units designed to perform the functions describedherein, and/or a combination thereof. The control module 16 alsoincludes one or more storage mediums. A storage medium can include oneor more memories for storing data, including read only memory (ROM),random access memory (RAM), magnetic RAM, core memory, magnetic diskstorage mediums, optical storage mediums, flash memory devices and/orother machine readable mediums for storing information.

The user interface 18 provides a means for a location user to interactwith the meter unit 6-1 and can include, for example, a display, one ormore lights, and a keypad. The user interface 18 can provide a paymentinterface including a currency receiver for receiving coins and/or billsfrom a user in payment for using the parking location, as well as areader for processing credit cards, debit cards, payment tokens, orproximity cards like Paywave™ and Paypass™ or NFC solutions like GoogleWallet™ and the like. The control module 16 is coupled to the userpayment interface and is configured to receive payment informationregarding the amount of a payment and/or card or token informationreceived at the payment interface. The control module 16 communicatesthe payment information from the user interface 18, via the radiotransceiver 12, with the remote data manager. The one or more lights ofthe user interface 18 can be used as an indicator as to the paymentstatus or, as discussed further below, can be used to produce anindication that a parking space that is associated with the location ofthe meter 10 is occupied.

In this example, the low-power sensor comprising the proximity sensor20, and the directional sensor 22, are located within or attached to theremovable meter unit 6 of the parking meter 10-1. Alternatively, theproximity sensor 20 and the directional sensor 22 could be located onanother portion of the meter 10-1 and/or could be located on the pole 8.The proximity sensor 20 is coupled to the control module 16 andcommunicates a trigger signal to the control module 16 when a proximitymeasurement exceeds a threshold level. Upon receiving the trigger signalfrom the proximity sensor 20 the control module 16 wakes up thedirectional object sensor 22 such that the directional object sensor 22can verify if an object is not only located near the parking meter 10-1,but is located within a parking space associated with the parking meter10-1. The directional object sensor 22 can be an optical sensor (e.g., adigital camera), a passive infrared sensor, a radar sensor, an activeinfrared sensor, or the like.

FIG. 2B shows functional block diagrams of an exemplary removable meterunit 6-2 and a tag 3 that can be used in meters such as the meters 10-2and 10-3 of FIGS. 1B and 1C. The meter unit 6-2 includes similarcomponents to the meter unit 6-1 in FIG. 2A, including the radiotransceiver 12, the antenna 14, the control module 15, the userinterface 18, the proximity sensor 20 and the directional object sensor22. In addition, the meter unit 6-2 also includes a short rangeinterface 11 by means of which it communicates with the tag 3. The tag 3has a short range interface 13, an ID module 15, and an optional memorymodule 17 for storing information regarding operating parametersincluding a payment collection history and/or configuration settings.The ID module 15 stores a unique identifier, e.g., a serial number, thatis associated with the tag 3.

The meter unit 6-2 is linked to the tag 3 for data communications by alink 37. In the case where the tag 3 is a wired tag 3-1, the link 37 isthe wire 5 (see FIG. 1B). In the case where the tag 3 is a wireless tag3-2, the link 37 can be a radio link or an optical link (FIG. 2B). Inthe case of a wireless tag 3-2, the short range interfaces 11 and 13 canbe any type of near-field communication (NFC) devices such as, forexample, RFID devices, Bluetooth devices, WiFi devices, IR devices, andthe like.

The proximity sensor 20 and the directional sensor 22 operate similarlyin the meter unit 6-2 as in the meter unit 6-1 described above. In analternative arrangement, not shown, the proximity sensor 20 and/or thedirectional object sensor 22 can be co-located with the housing 2, thetag 3, the cash box 4 or the pole 8. In these arrangements, theproximity sensor 20 and/or the directional object sensor 22 can becoupled to the short range interface 13 of the tag 3 or to another shortrange interface so as to communicate detection signals to the controlmodule 16.

In one embodiment, the control module 16 communicates the paymentinformation, via the link 37, to the short range interface 13 of the tag3. The short range interface 13 then updates the optional memory module17 based on the received payment information. The memory module 17 canadd the amount of currency indicated to have been received by thereceived payment information to the stored amount. This is useful whenthe meter unit 6 is swapped for maintenance reasons as thereby coincounts can be transferred to the replacement meter unit and the coinaudit reliability is maintained. In addition, the memory module 17 canalso receive and store transaction-time information including the dateand time of day that the payment was received. In one aspect of thisembodiment, the control module 16 communicates time of day informationof when a vehicle enters and leaves a parking spot, as detected by theproximity sensor 20 and the directional object sensor 22, to the tag 3.

FIG. 3 shows an example configuration of a group of parking meters 10equipped with the proximity sensor 20 and the directional object sensor22 and positioned near single-space parking spaces 50. The parkingspaces 50 in this example are diagonal pull-in spaces, as indicated bythe solid lines angled from the lateral lines indicating a curb orstreet edge. The directional object sensor 22 in each of the respectivemeters 10 is positioned and calibrated such than an object such as avehicle that moves into a position in proximity to the meter will entera space within a directional cone 24 indicated by dashed lines. Thedirectional cone 24 is a space that is projected outwardly from theassociated parking meter 10 and towards the specific parking space 50associated with the parking meter 10 and with which the directionalobject sensor 22 is associated. An object, such as a vehicle, thatenters the area of the directional cone 24 will be detected, first bythe low-power proximity sensor 20, which detects the presence of theobject of interest, and which then triggers the higher power directionalobject sensor 22. The directional object sensor 22 receives powersufficient to make a determination for confirming the presence of avehicle in the parking space 50.

FIG. 4 shows another example configuration of a group of parking meters10 equipped with the proximity sensor 20 and the directional objectsensor 22, where the meters 10 are positioned near parallel parkingspaces 50. That is, the parallel parking spaces are oriented parallel tothe lateral curb or road edge depicted in FIG. 4. The directional cones24 can be calibrated digitally by setting directional gains to enhancesignals within predetermined areas for the detection of objects ofinterest, such as vehicles attempting to park. Alternatively, thedirectional object sensors 22 could be positioned and/or shielded toproduce the desired directional cone 24.

A process for operating a parking meter 10 equipped with a low-powersensor 20 such as a proximity sensor and a directional sensor 22 cancomprise the following operations (not necessarily in the order listed):

-   -   1. detecting an object in proximity to a parking meter with a        low-power sensor coupled to the parking meter; if, for example,        the low-power sensor is a magnetometer, then the object is        detected based on a change in a magnetic field at the meter;    -   2. in response to the trigger event, activating a directional        sensor;    -   3. receiving sensor data at the directional sensor from a        predetermined direction relative to the meter;    -   4. determining a presence of an object, or lack thereof, in the        predetermined direction based on the received sensor data; and    -   5. upon a determination of the presence of the object, storing        an indication of the presence of the object along with a time of        the determined presence.

A threshold change in the magnetic field that results in detection ofthe object can be determined empirically. A time threshold can also beused (if change in magnetic field lasts for more than a threshold time).The magnetic field threshold and the time threshold can vary on theconfiguration of the parking space and the orientation of the parkingmeter. The sensitivity and directional gains, which can be used to tunethe aim of the directional sensor, can also be determined empirically.Adaptive algorithms could be used to fine-tune the time threshold, theproximity sensor detection levels and the directional gains associatedwith the directional sensor.

Determining the presence of the object based on the received sensor datacan include determining a confidence measure and/or a margin of errormeasure. For example, if the directional sensor is an ultrasonic sensor,the ultrasonic sensor receives an echo representative of a size anddistance of the object. A valid vehicle detect status may be, forexample, an echo from a large object at a distance between 3.0 feet and9.0 feet. A large object at 5.0 feet would be in the middle of theexpected parameters and would have a higher confidence or a smallermargin of error than a smaller object at, for example, 3.0 feet.Similarly visual detection could evaluate the size and position of theobject against an expected vehicle size. The meter can vary subsequentactions depending on the confidence measure and/or the margin of errormeasure. For example, the meter may only report a parking violation ifthe vehicle presence detection is above an 80% confidence value.

In addition to detecting the object in proximity to the parking meter,the low-power proximity sensor could be used to detect when the objectsubsequently departs the proximity of the parking meter. For example, ifthe proximity sensor is a magnetometer, the control module coulddetermine a change in magnitude of the magnetic field from a baselinevalue, where the baseline value is a value indicative of no object beingin proximity to the parking meter. The magnetometer measurement can be aone, two, or three degrees-of-freedom (DOF) measurement that includesdirection(s). Subsequent to the initial change in magnitude anddirection of the magnetic field, the control module can detect anopposite change in magnitude and direction of the magnetic field anddetermine that the object has departed the proximity of the parkingmeter.

In embodiments that use a magnetometer, a baseline measurement can bedetermined as follows. A three DOF magnetometer returns a vector, (x, y,z), that represents the magnetic field around the meter. The baselinemeasurement represents an expected measurement vector (along x, y, zaxes) when no vehicle is present in proximity to the meter. The baselinecondition can be time-adapted to absorb a change in the environmentalmagnetic field or a shift in the measurement offset. Occasionally, thebaseline measurement is not set or has drifted beyond a tracking window.In that case, it is beneficial to automatically determine a new baselinevalue without knowing when a vehicle is absent or present. Thetraditional way of doing this is to have a person visit the parking siteand command the meter to determine a new baseline when no vehicle ispresent. This is time-consuming, especially in areas where there is ahigh occupancy rate and one must wait for a vehicle to depart.

An alternative way of determining a new baseline measurement when novehicle is present is to have the control module of the meter receivethe (x, y, z) measurements from the magnetometer after each step-changein readings. The (x, y, z) measurements are stored in a memory coupledto the control module. When sufficient measurements are captured over aminimum time period, the measurement data is analyzed to find a singlecluster of readings. Because each vehicle has a different magneticsignature, the magnetic field measurement values obtained when one ormore vehicles are present in proximity to the meter will be scatteredsubstantially across the (x, y, z) space. The baseline measurements thatcorrespond to no vehicles being present should generally be in a singlecluster group in the (x, y, z) space. The center of the clusteredmeasurements is determined and used as the new baseline measurement.That is, an object can be detected by comparing the proximitymeasurement to a baseline measurement, wherein the baseline measurementrepresents an expected proximity measurement when the object is notpresent, such that the object is deemed to be positively detected if theproximity measurement differs from the baseline measurement by more thana threshold value. The threshold value can be set depending on theenvironmental factors of the installation and types of vehicles to bedetected.

The parking meter 10 described above includes a low-power proximitysensor 20 and a separate directional sensor 22. An alternative parkingmeter could use a single sensor including a low power proximity sensorintegrated with a directional sensor. The integrated sensor wouldoperate in a low power mode with only the low-power proximity sensoractive and, when the proximity sensor detects an object in proximity tothe meter, the directional sensor would be activated to detect thepresence of the object in a predetermined location relative to themeter. Yet another alternative parking meter could use a single sensorthat operates in a low-power mode and in a high-power mode. In thelow-power mode, the single sensor of this alternative would be able todetect an object in proximity to the meter, but would not be able todetect the location of the object relative to the meter (anomnidirectional mode). In the high power mode, which would be activatedwhen the sensor in the low-power mode detects an object, the singlesensor would be switched to the high-power mode in order to sense thelocation of the object relative to the meter (a directional mode).

We claim:
 1. A method of operating a parking meter, the methodcomprising: (a) detecting an object in proximity to a parking meter by aproximity sensor, the detecting being based on a change in a proximitymeasurement at the meter, wherein the proximity sensor is selected fromthe group consisting of: a radio transceiver, a magnetometer, an opticalsensor, and a pressure sensor; (b) activating a directional sensor inresponse to detecting the object; (c) receiving sensor data at a meterprocessor from the directional sensor, the received sensor dataindicating a predetermined direction to the detected object relative tothe parking meter; (d) determining a presence of the object, or lackthereof, in the predetermined direction based on a proximity measurementby the proximity sensor and the sensor data; and (e) upon adetermination of the presence of the object, or the lack thereof,storing an indication of the presence of the object, or the lackthereof, along with a time of the determination.
 2. The method as inclaim 1, wherein the proximity sensor is a magnetometer coupled to theparking meter and wherein the proximity measurement is indicative of amagnetic field at the parking meter.
 3. The method as in claim 1,further comprising in (d): determining a confidence level of thepresence of the object in a space associated with the parking meterbased on the proximity measurement and the received sensor data; andsubsequent to determining the confidence level, varying an action of themeter based on the confidence level.
 4. The method as in claim 3,further comprising: comparing the proximity measurement to a baselinemeasurement, the baseline measurement representing an expected proximitymeasurement when the object is not present; and positively detecting theobject present if the proximity measurement differs from the baselinemeasurement by more than a threshold value.
 5. The method as in claim 3,wherein the varying the action comprises: resetting time remaining onthe parking meter to zero or another desired amount.
 6. The method as inclaim 3, wherein the varying the action comprises: updating paymentinformation associated with the object on a memory module of the meter.7. The method as in claim 1, further comprising, prior to (a),determining a presence of the object in proximity to the parking meter.8. The method as in claim 1, wherein the directional sensor is at leastone of: (a) an ultrasonic sensor, (b) an optical sensor, (c) a passiveinfrared sensor, (d) an active infrared sensor, and (e) a radar sensor.9. The method as in claim 8, wherein the optical sensor is a digitalcamera.
 10. The method as in claim 1, wherein the directional sensor iswirelessly connected to the meter.
 11. The method as in claim 1, furthercomprising: tuning the directional sensor by varying sensitivity anddirectional gains for the directional sensor.
 12. The method as in claim11, wherein the sensitivity and directional gains are determinedempirically.
 13. A parking meter comprising: (a) a proximity sensorconfigured to detect an object in proximity to the parking meter basedon a proximity measurement, and configured to produce a trigger signalin response to the detection of the object, wherein the proximity sensoris selected from the group consisting of: a radio transceiver, amagnetometer, an optical sensor, and a pressure sensor; (b) adirectional sensor configured to detect the object in a predetermineddirection relative to the parking meter; and (c) a control modulecoupled to the proximity sensor and the directional sensor andconfigured to: i. receive the trigger signal from the proximity sensorand, in response to receiving the trigger signal, activate thedirectional sensor, ii. receive sensor data from the directional sensor,iii. determine a presence of the object, or lack thereof, in thepredetermined direction based on the proximity measurement and thereceived sensor data, and iv. upon a determination of the presence ofthe object, or lack thereof, store an indication of the presence of theobject, or lack thereof, along with a time of the determination.
 14. Theparking meter as in claim 13, wherein the directional sensor is at leastone of: (a) an ultrasonic sensor, (b) an optical sensor, (c) a passiveinfrared sensor, (d) an active infrared sensor, and (e) a radar sensor.15. The parking meter as in claim 14, wherein the optical sensor is adigital camera.
 16. The parking meter as in claim 13, wherein thecontrol module is further configured to determine a confidence level ofthe presence of the object in a space associated with the parking meterbased on the proximity measurement and the received sensor data.
 17. Theparking meter as in claim 16, wherein the control module is furtherconfigured to, subsequent to determining the confidence level, vary anaction of the meter based on the confidence level.
 18. The parking meteras in claim 17, wherein the action of the meter is to reset timeremaining on the parking meter to zero or another desired amount.